It was a typical day at the Denver Mint in 1979. Presses were busy in a cycle that repeated itself over and over, faster than the human eye could register. At one press, striking 1979-D Lincoln cents, planchets were dropped, one-by-one, onto the anvil die. With each repeat of the cycle, the hammer die slammed into the waiting planchet with tons of force as the surrounding collar rose up to encircle the planchet during striking. An instant later, the newly struck coin was ejected from the coining chamber and a new planchet dropped into place — the hammer die slammed, the collar rose, newly struck coin ejected, over and over and over, all behind the safety shield designed to protect workers in case something broke, with the potential of creating shrapnel from the planchets or parts of the press.

Something went wrong.

A cent planchet dropped into place and was struck between hammer and anvil dies, but it was not ejected. Instead, it remained stuck inside the coining chamber, most likely adhering to the anvil die. A new planchet was fed into the press and it, too, was struck, though not by both dies. Instead it was struck by one die — the hammer, probably — and by the stuck cent, now serving as a die cap. This new cent failed to be ejected but was bonded to the first cent. New planchets were fed into the press one by one, over and over, with the same unintended result, as coins began to be bonded together in what was becoming a massive cluster of cents. As the cluster grew, previously struck cents became increasingly distorted as they began wrapping around the shaft of the still working hammer die. The cluster of coins spread out until one final planchet was dropped onto the top of the clump of cents and struck, forming a nearly perfect face of the obverse. Then the press stopped — on its own accord or when a Mint worker noticed the accumulating cluster of cents or a change in sound as the routine clangs of coins being struck became clunks as the cluster grew. The cluster was removed: a beautiful monstrosity, a Frankenstein’s Monster of a coin, an error.

No hypothetical scenario

The scenario just described is no hypothetical one. A multiple-strike 1979-D Lincoln cent die cap cluster was produced at the Denver Mint. It escaped the facility (though by all rights it should have been detected and if not resigned to the melting pot, at least kept within the confines of the granite structure at Colfax and Delaware streets, maybe for display for future visitors). However, such pieces can escape the Mint, a shown by this piece, which appeared in Stack’s Bowers Galleries’ Aug. 9, 2012, Rarities Night Auction as lot 11638.

The lot description was brief. As the cataloger wrote, “Words alone do not suffice on an error of this magnitude, so readers are directed to the photo to enjoy a better understanding of the scope of the error. Definitely one for the record books!”

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The cluster is a mass of distorted cents, all jagged edges and rounded edges blending together from cent to adjacent cent, with an off-center hole representing where the stresses of repeated blows of the dies tore a portion of the cluster apart. A nearly perfect obverse face of the last coin struck identifies the coins as 1979-D cents, while on the opposite side of the cluster a distorted though still identifiable Lincoln Memorial design is visible. The cluster is an inch or so thick and about 2 inches wide. It weighs 105 grams, suggesting that 33 or 34 3.11-gram cents form the mass of copper and zinc. It was probably created in less than a minute, given the speed at which circulating coins are struck using modern minting technology. 

The cluster sold for $10,925 at the auction including buyer’s fee.

A somewhat smaller cluster of bonded 1999 Lincoln cents was offered in Stack’s Bowers’ June 2014 Baltimore Expo auction. As Coin World’s Steve Roach reported after the auction, “Among errors, few are more dramatic than multicoin bonded clusters where multiple strikings fuse planchets together resulting in a massive single object. 

“In this spectacular error, more silver-colored zinc is visible than rich copper, and the center strike is boldly impressed on the obverse. The different colors are the result of a switch in 1982 for Lincoln cents, from a copper-based composition to a composition having a core of 99.2 percent zinc, .8 percent copper and a plating of pure copper. 

“The reverse design is only lightly impressed, with lettering seen on the peripheries, as the central part of the piece was flattened due to the multiple strikings and the flow of the metal outwards. 

“Most bonded planchet errors are generally caught by the Mint and destroyed, so one that is this substantial is unusual in the marketplace. As Stack’s Bowers notes, examples like this one ‘capture the force of the strike and coining process when things go slightly wrong.’

“In terms of valuation, errors of this type that can fit into standard sized slabs are often easier for dealers to market than pieces that won’t fit into slab. PCGS has graded this one MS-64 red, and the weight of 156 grains noted on the slab converts to 10.11 grams. Since a normal 1999 copper-plated zinc cent weighs 2.5 grams, one can deduce that the cluster has four or five coins. It sold for $2,702.50.”

The beauty of error coins

Error coins result when something goes wrong during the minting process, whether during the creation of the alloy, the production and processing of blanks and planchets, or the striking process itself. Errors can be as mundane as a minor grease-filled die piece to as spectacular as a 34-coin cluster of cents or a “mule” struck from the wrong combination of dies or edge devices.

All are collectible to one degree or another — some carry no premium while some of the wildest and rarest errors can sell for six-figure prices.

Let’s get some basic terminology out of the way first. 

At its most basic level, an error coin is one that deviates from the standard due to a mishap in the minting process. Error collectors have traditionally classified them in three broad categories — striking errors, those pieces that result from a mishap during the actual striking of the coin; planchet errors, or those created due to a mishap during the production, processing or selection of the planchet; and die errors, or those pieces that reflect an error involving the die itself. This article will not feature a subset of the latter called die varieties, or pieces like the famed 1955 Lincoln, Doubled Die Obverse cent, produced from a die bearing spectacular doubling that resulted during the creation of the affected die.

Why do some collectors gravitate toward error coins and not the normal pieces most collectors covet? Douglas Mudd, curator and director of the American Numismatic Association Edward C. Rochette Money Museum, discussed some of the reasons in his foreword to the Whitman book 100 Greatest U.S. Error Coins.

“These ‘bloopers’ create a wonderful collecting opportunity, much to the delight and fascination of collectors,” he writes, adding that the ANA Money Museum’s exhibit of error coins “was one of the most popular exhibits we have ever created” and that the ANA has had more questions about errors than any of the other coins and paper money in the association’s other exhibits (the same holds for Coin World; we receive questions about suspected error coins every week). Visually, error coins like off-center cents, wrong planchet pieces and double-struck coins draw the eyes of even noncollectors in ways “normal” coins might not. 

While this article cannot be all inclusive, here are some favorite error types.

Broadstrikes

Minting technology has come a long way since humans began producing coins some 2,600 years ago by casting them in molds or hand-striking misshapen blobs of metal against a hard surface, using a punch to form a design on one side. For centuries, no or little effort was taken to make the flans or planchets uniform in shape; it was more important that the weight of each coin met established standards. Even when the first true coinage dies were introduced, coins were misshapen, not only because of the lack of uniformity in planchet shape, but because the metal of the coin could expand outward during striking because nothing was in place to restrict outward flow.

That changed in the late 16th century with the introduction of the “collar” — a steel ring into which a now uniformly round blank was placed. The collar restrained outward metal flow during striking, resulting in perfectly round coins — except when the collar was not present during the blow of the dies.

A broadstruck coin, or broadstrike, is a piece struck outside the confines of the collar. The metal of the planchet was able to spread outward, beyond what is now considered a coin’s normal diameter, and, because no collar was present during striking, the coin lacks any special edge device, like reeding. Some broadstrikes were well centered between the dies, while other broadstrikes were partially outside of the area between the faces of the dies.

The illustrated 1883-O Morgan dollar is an uncentered broadstrike, struck outside of the collar. It was described as follows in the Heritage auction where it was sold: “The entire design is present, though the coin’s unstruck areas are primarily above and to the left on the obverse.” 

The coin, graded Mint State 64 by Professional Coin Grading Service, sold for $2,300 in the October 2008 auction.

This coin shows faint signs of bifurcation along the unstruck regions, or a distortion of the design elements along the edge. This bifurcation results from the unrestrained metal flow during striking, with elements like the dentils and some of the letters in E PLURIBUS UNUM showing slight distortion.

In a normal strike that is confined by the collar, the dies strike the planchet and the metal flows outward only until it snugs up against the collar; no distortion of peripheral design elements occurs. But when the collar is not present, the dies strike the planchet and the metal flows outward, unrestrained, pulling bordering struck design elements along, in the path of least resistance. This unrestrained outward flow can result in design distortion.

The illustrated broadstruck 1965 Washington quarter dollar (taken from a Special Mint set) shows a great deal more distortion than the Morgan dollar. Look at the date on the obverse, and how it appears to slide outward toward the edge of the coin. Similar distortion of the inscriptions appears on the reverse.

The coin realized $1,057.50 in an October 2012 Heritage auction, where it was graded MS-66 ? by Numismatic Guaranty Corp.

Not all broadstruck coins are going to bring high prices. It is relatively easy to find broadstruck Lincoln cents on eBay for a few dollars, the low prices reflecting the abundant supply of those errors in the. These common versions of the error are a great place for new collectors to start.

Off-center coins

Sometimes a planchet is deposited partially off-center so it does not lie perfectly centered between the obverse and reverse dies. The result can be an off-center coin that, as the name implies, was struck partially off-center.

The 1904 Coronet gold $20 double eagle is only 15 percent off-center (not a large degree) but what the coin lacks in its degree of off-centeredness, it makes it up in being the largest gold denomination struck for circulation. The size of the coin and the fact that it is made of gold makes it a highly desirable piece.

According to the Heritage Auctions catalog description for the coin (it appeared in the firm’s April 2014 Central States Numismatic Society auction), “The 2010 Whitman reference 100 Greatest U.S. Error Coins ranks this remarkable double eagle as #7, the highest rank of any off-center error.”

The cataloger added that the coin was discovered in Switzerland in the 1990s, in a “collection [that] had apparently been buried for decades, a relatively common occurrence during World War II.”

“The off-center strike affects S OF AMER, with the tops of those letters off the flan. The reverse peripheral legend exhibits the bifurcation toward the rim typical of an off-center error, since no collar die is present to restrain metal flow toward the border,” the catalog adds.

The struck portions of the coin represent the area of the planchet that lay between the dies during striking while the crescent of unstruck metal lay outside the plain of the dies. Note on both sides how the rim did not strike up and the dentils are soft and incomplete directly adjacent to the unstruck crescent, suggesting that the outer edge of the die did not make full contact with the planchet.

This coin sold for $79,313.01 by Heritage.

Collectors should not assume, however, that all off-center coins bring five-figure prices. On the contrary, many off-center coins sell for just a few dollars each. I remember seeing bags of hundreds of off-center Lincoln cents at an error dealer’s bourse table at a major coin convention, with the errors all priced at a dollar or two. With Lincoln cent mintages in the billions most years, it is not surprising that thousands of off-center strikes would escape the Mint and make their way into the marketplace.

Older off-center coins can bring prices that fall between the two extremes outlined here. Take, as an example, the 1863 Indian Head cent shown here. It sold for $218.50 in a 2005 Heritage auction, more than a dollar or two, but still well within many collectors’ budgets. 

The coin was struck about 12 percent off-center and apparently was deemed “normal” enough that it received considerable circulation wear; it was graded Good 6 by Professional Coin Grading Service. As the cataloger noted, “One might wonder how a coin being struck off center this much managed to remain in circulation long enough to grade Good.” 

The wear adds charm to the coin, at very affordable price for the successful bidder.

Die caps

We began this feature with descriptions of bonded clusters, formed as one coin after another is struck and then retained inside the coining chamber until a mass of distorted coins is created. But what happens when a coin remains within the coining chamber while subsequent incoming planchets each are struck and ejected?

The result can be a die cap like the illustrated 1859 Indian Head cent.

When this coin was struck, instead of being ejected, it stuck to the obverse. The coin remained attached to the obverse die for at least several strikes, as witnessed by its bottle cap shape.

As the stuck coin struck incoming planchets, the metal began to flow upward over the shaft of the obverse die, forming a cap shape. At the same time, the reverse side of the coin, facing incoming planchets, became increasingly distorted from its repeated blows against the planchets. However, after three or four strikes, this cap popped loose and was ejected from the dies.

During this coin’s time as a die cap, it blocked the incoming planchets from coming into contact with the obverse die. The reverse of the cap, facing those planchets, served as a surrogate die and created yet another error category — brockages (which we will get to next, so hold on).

How can we tell that the cap struck just a few coins before becoming dislodged? Look at the reverse. The ONE CENT is readable but distorted and so large that it fills the face of the cap. Had it been in use much longer, the repeated blows against incoming planchets would have obliterated the design elements. 

The unusual shape of the coin makes it a favorite among collectors. “Few errors are so visually arresting as a well-preserved die cap,” notes the Heritage catalog description. 

Unlike the off-center Indian Head cent discussed earlier, this piece must have been saved by someone as soon as it entered circulation. Heritage writes, “In addition to showing all the classic aspects of an obverse die cap, including tall walls, a hyper-detailed obverse impression, and a strongly distorted reverse, at the MS66 grade this is one of the best-preserved 1859 cents out there, die cap or not, with the 1859 cent’s status as a one-year type adding to the coin’s importance.”

The coin sold for $23,500 in the Heritage March 2014 U.S. Coins Signature Auction.

The 1895-O Barber dime is another example of a die cap that struck only a few coins before becoming dislodged from the obverse die, as illustrated by a slightly distorted reverse design. The central denominational inscription is larger than normal and the outer edges of the wreath have started to bend upward as the metal of the coin migrated along the shaft of the obverse die.

This piece, graded MS-64 by PCGS, sold for $16,450 in a Heritage auction earlier in 2016.

Brockages

So, what about the coins die caps strike? Are they errors? Yes, they are. In fact, two different kinds of errors are attributed to being struck by die caps.

The most spectacular form of error derived from a die cap is called a brockage, and it results from the coin being struck by the side of the die cap facing incoming planchets.

Since the die cap blocks the die the coin is stuck to, the opposite face of the cap serves instead as the surrogate die, and since the design elements on the die cap are right facing and raised, they transfer to the incoming planchets as mirror images and incused — a brockage. Moreover, the brockage is a mirror to the design struck by the unimpeded die, so the coin has the same design on both sides, only with one side normal and the other a mirror version.

Look, for example, at the illustrated large cent brockage. The normal reverse is accompanied by the brockage reverse in the form of an incused mirror image. It is clear, too, that this was a first strike brockage since the design shows no distortion (just as the face of a die cap becomes distorted from multiple strikes, so do the brockage images struck by the cap; the first strike is a perfect mirror image, with subsequent brockage strikes increasingly distorted).

Another interesting point about this coin is that, even lacking an obverse design, the coin can be attributed not only by date but by Newcomb die variety.

Heritage explains, “The obverse of this cent shows a perfect brockage of the reverse, but the cent can nonetheless be attributed by Newcomb variety due to the spike from the leaf above the O in ONE, repunching on the E in CENT, a delicate die crack connecting the tops of TED, and the base of the E above the M in AMERICA. The reverse die only struck 1828 N-5.”

Heritage further explains an anomaly on one side, “On the brockage side, an arc of raised surface obscures a portion of AMERICA (the cent acting as an obverse die was presumably laminated in that area).”

This coin saw light circulation before being saved in someone’s collection. The Heritage cataloger gave the coin a grade of Extremely Fine 45 based on standards used by Early American Coppers, a club for fanciers of large cents and other early copper coinage of America. PCGS graded the coin About Uncirculated 58 using its standards. (It is not unusual for an EAC grade to be lower than a commercial grade, given the different approaches to grading by the club and the commercial grading services.)

This remarkable brockage error sold for $5,640 in Heritage’s just closed American Numismatic Association Signature Auction in Anaheim, Calif.

Obverse brockages are also possible, as illustrated by the undated Indian Head gold dollar (of the first Indian subtype, also called the Small Head design or Type II) shown here. The date appears on the reverse of all three design types of U.S. gold dollars, but with the current state of research into die varieties of the series, catalogers were unable to identify the date of this particular coin.

Like the 1828 large cent, this coin appears to be a first strike brockage given the lack of any design distortion on the brockage side.

Heritage writes: “One of the most extraordinary lots in the auction, this dateless example has a normal Type Two gold dollar obverse but an incuse mirror image (brockage) on the reverse. Gold-orange surfaces are lightly rubbed, as if the coin had been carried as a pocket-piece for a brief time. Errors on gold coins are extremely elusive, and when found, tend to be minor (such as a slight clip or off-center strike). To have a full, clear brockage on a Type Two gold dollar is an exceedingly rare delight, and the knowledgeable collector of error coins will bid accordingly.”

The coin, graded AU-55 by PCGS, realized $38,187.50, a big price for such a tiny coin. The error appeared in Heritage’s April 2014 CSNS Signature Auction.

As referenced earlier, a second type of error coin can be generated from a die cap. When the design is obliterated on a cap by repeated blows against incoming planchets, the cap ceases to strike brockages and instead produces capped die strikes. Eventually, as the metal of the cap thins, details of the die it obscures can leak through the cap, and faint images of the obscured die begin to appear on the capped die strikes. With each succeeding strike, more and more of the obscured design is formed on the new coins until eventually the die cap is destroyed and any remnants fall from the press.

Multiple-struck errors

A number of the errors discussed so far occurred when a coin was not ejected from the coining press. A particular kind of coin called a multiple-struck error occurs when a coin is struck once and then remains inside the coining chamber (either centered on the die or partially outside) and is struck one or more additional times.

The 1945-S Walking Liberty half dollar shown here was struck twice, the first time normally and the second time 55 percent off-center, with the overall result a striking example of a striking error.

Heritage writes: “This exact coin is plated under #36 in the 2010 edition of 100 Greatest U.S. Error Coins, where it is described as ‘the most dramatic multi-struck Liberty Walking half dollar known.’ After the normal first strike, the piece failed to fully eject from the dies. It was struck again, widely off center, toward 6:30. The second strike is centered at 8:30 relative to the first strike. The mintmark is visible from the first strike where the two strikes overlap.”

The error realized $41,125 in Heritage’s November 2013 U.S. Coins Signature Auction in New York City. The coin is graded MS-63 by PCGS. Heritage notes, “This dramatic mint error is satiny and bagmark-free, and exhibits delicate ice-blue and chestnut-gold toning. A coin counter has left an inconspicuous patch of hairlines on the eagle’s right (facing) wing from the first strike.”

While double-struck coins like the half dollar are spectacular, another category of double-struck coin is maybe even more interesting.

Double-denominations

Congress never authorized an 11-cent coin, yet genuine 11-cent coins (of a sort) do exist as errors — one of a number of errors called double-denominations.

U.S. Mint facilities strike coins of different denominations at the same time, generally on presses in close proximity, and sometimes, struck coins of one denomination find their way into a press set up to strike a different denomination. The result is a double-denomination error.

Probably the most commonly encountered double-denomination error is the 11-cent coin, so nicknamed because a struck dime was struck a second time but between cent dies. Both denominations are struck in large quantities, accounting for a relative abundance of the error.

The illustrated cent-dime combination is a great example of the error category. It is made even more special because not only was the coin struck by two different die pairs of different denominations, the dies were of different dates.

A 1995-P Roosevelt dime was struck first, then the coin made its way into a second press where it was struck by 1996 Lincoln cent dies. That suggests that the dime was struck late in the production year and may have become trapped in a bin or other container that was reused in early 1996 to hold cent planchets. The dime began dislodged and was fed into the cent press along with the regular cent planchets.

Double-denomination errors can have a striking appearance and this coin is a perfect example of why. Abraham Lincoln’s portrait overlaps the portrait of Franklin Roosevelt on the obverse, and the Lincoln Memorial is impressed over the dime’s torch on the reverse. 

As for the dates, Heritage writes, “The 1995-P dime date is sharp except for the final digit, which is nonetheless apparent. The 96 in the cent date is also evident.”

The firm added detail about the positioning of the overlapping designs, “Roosevelt gazes toward 7 o’clock relative to the portrait of Lincoln. The flame of the dime torch overlaps the east wing of the Lincoln Memorial.”

The presence of two different dates on a double-denomination is unusual; most often, the designs are of the same date.

This 11-cent coin, graded MS-64, realized $1,880 in an August 2015 auction by Heritage, a somewhat affordable error for collectors who have a bit of money to spend on errors. The price was a bit higher than a similar cent-dime combination (but with both coins dated 1996) also sold by Heritage but graded NGC MS-67; that piece sold for $1,380 in March 2010. The novelty of two different dates possibly accounts for the higher price of the lower-grade piece.

Almost any combination of double-denomination can be created, though, typically, the original coin has to be smaller than the second strike, at least in an unaided error. In the case of a cent-dime denomination, the dime is smaller than the cent in physical size and thus would pass through the feed mechanism. However, it is less likely that a cent would be a first strike and a dime a second strike, since the cent would likely be too large to fit through a dime feed mechanism. Still, some “errors” are known in which a smaller coin is struck over a previously struck larger coin. It is likely that many if not most such pieces are deliberately struck by a Mint employee. It is unlikely, for example, that a half dollar would be fed between cent dies, since the feed mechanism for the smaller coin would never accept the large coin. Yet, such pieces do exist. While such pieces are genuine, though likely of assisted birth, they are generally collected avidly alongside unintentional errors. 

The undated Washington quarter dollar struck over an undated Lincoln cent is another attractive unintentional U.S. double-denomination.

The coin predates the State quarter dollars program and the reverse of the cent is of the Lincoln Memorial design, which narrows the date range somewhat. 

Heritage writes: “For the strike as a quarter, the centering favors the portrait and eagle with the date off the flan. The cent date was on the field near Washington’s nose but was effaced by the quarter strike. Lincoln’s shoulder and much of the Lincoln Memorial remains from the first impression. No quarter mintmark is apparent near the ribbon or below the wreath.”

The coin, graded MS-64 red by NGC, sold for $3,525 at Heritage’s January 2016 Signature Auction at the Florida United Numismatists convention auction.

Heritage adds, “The peach-red color is unmellowed. No marks or spots are readily apparent. No weight is recorded on the NGC insert, but the mint error appears to be bronze instead of copper-plated zinc,” the latter further narrowing the date to 1982 or earlier.

Another popular combination is a “6-cent coin,” or a coin struck by both cent and 5-cent piece dies.

A good example of that error was offered in Heritage’s August 2011 U.S. Coins Signature Auction at the American Numismatic Association World’s Fair of Money.

The coin started as a 2000-D Lincoln cent. It then made its way to a press striking 2000-D Jefferson 5-cent coins.

The random placement of the cent between the 5-cent coin dies resulted in the larger coin’s obverse being struck over the smaller piece’s reverse and vice versa, with the cent rotated 90 degrees in relation to the 5-cent coin’s designs. 

Jefferson’s portrait is impressed over the Lincoln Memorial, with only portions of the inscriptions from the cent still readable. Both central devices are strong, however. Inscriptions from both pieces are incomplete or weak because of the error.

The other side of the piece shows the Jefferson Memorial virtually obliterating Lincoln’s portrait (the cent was turned at a 90 degree angle when struck, so the portrait and building line up perfectly). The 5-cent coin’s motto E PLURIBUS UNUM is incomplete because the cent presented too small a palette to display the full design of the larger denomination.

The coin, graded MS-64+ by PCGS, realized $1,150 in the 2011 auction.

These are just a few of the many kinds of error coins. For a weekly look at errors, do not miss the Collectors’ Clearinghouse column by expert Mike Diamond in the weekly issues of Coin World.

Error collecting can be fun but it does not have to be expensive. While it is true that larger coins like half dollars and dollars tend to bring higher prices than more plentiful cents and 5-cent coins, and gold coin errors more than Lincoln cent errors, many affordable pieces exist.

A collector who sticks with Lincoln cents, for example, can purchase many error types for less than $100 and often for less than $10 (we’ve already described a few such examples). One can start with these inexpensive pieces and later advance to more expensive coins. However, as one begins collecting the pricier coins, it becomes important to buy only certified pieces since many counterfeit errors are in the marketplace, many of them produced by private firms in China. Still, do not let the fear of buying a fake keep you from participating in a specialty that will keep you excited about collecting for years.